This invention relates to a motion detector operating with a video signal. This invention also relates to an image stabilizing system usable in video equipments such as a video camera.
Movement of a video camera causes unwanted fluctuations of images represented by a video signal outputted from the video camera. Various systems have been developed to compensate for such unwanted fluctuation of images.
ITEJ Technical Report, Vol. 11, No. 3, pages 43-48, May 1987, discloses a prior art system for removing unwanted fluctuation of images represented by a video signal. In this prior art system, an analog input video signal is converted by an A/D converter into a corresponding digital video signal which is fed to a Y/C separation circuit and a delay circuit. The Y/C separation circuit separates a Y signal from the digital video signal, and the Y signal is fed to a motion vector detector. The motion vector detector detects motion vectors of images while being subjected to control of a detection region. Corrective vectors are generated on the basis of the detected motion vectors. The output video signal from the delay circuit is processed in response to the corrective vectors so that the positions of the images will be corrected in response to the motion of the images. This prior art system requires a large-scale circuit since the motion vector detector and other devices are complicated in design.
ITEJ Technical Report, Vol. 11, No. 28, pages 19-24, November 1987, discloses a prior art image stabilizing technology for a video camera. In this prior art technology, fluctuation of a television camera is detected on the basis of the output signals from angular velocity sensors, and an image pickup unit of the television camera is moved in response to the detected fluctuation so that images represented by the output signal from the image pickup unit can be independent of the fluctuation of the camera.
IEEE Transaction on Consumer Electronics, Vol. 36, No. 3, August 1990, which is not prior art to this invention, discloses an automatic image stabilizing system. In this background system, motion of images represented by an input video signal is detected as motion vectors by a motion vector detector, and the video signal is processed in response to the motion vectors so that the positions of the images will be corrected in response to the motion of the images to remove unwanted fluctuation from the images. This background system can be composed of a small-scale circuit since the motion vector detector and other devices are simple in design.
Under conditions where an image of an object is picked up by a television camera having a vertical sync frequency of 60 Hz and the object is illuminated by a light source powered by a 50-Hz ac line electric energy, the image represented by the video signal outputted from the television camera is contaminated by 20-Hz flickers. The previously-mentioned prior art system and background system lack a device for removing such flickers. Therefore, in the previously-mentioned prior art system and background system, generated motion vectors tend to be inaccurate when an input video signal is contaminated by such flicker components. Also, the previously-mentioned prior art technology lacks a device for removing flickers.